Intra prediction method and decoder

Abstract

An intra prediction method and a decoder are provided. The method includes the following. A prediction mode parameter is obtained, where the prediction mode parameter indicates that an intra prediction value is to be determined in a derivation manner. At least two prediction modes are determined according to the derivation manner. A first weight combination related to the at least two prediction modes is determined. A first cost for performing prediction on a template region of a current block in the at least two prediction modes is determined according to the at least two prediction modes and the first weight combination. A second cost for performing prediction on the template region in a first prediction mode is determined according to the first prediction mode. An intra prediction value of the current block is determined according to the first cost and the second cost.

What is claimed is: 
     
         1 . An intra prediction method, applicable to a decoder and comprising:
 obtaining a prediction mode parameter, wherein the prediction mode parameter indicates that an intra prediction value is to be determined in a derivation manner;   determining at least two intra prediction modes according to the derivation manner;   determining a first weight combination related to the at least two intra prediction modes;   determining a first cost according to the at least two intra prediction modes and the first weight combination, wherein the first cost is for performing intra prediction on a template region of a current block in the at least two intra prediction modes;   determining a second cost according to a first intra prediction mode, wherein the second cost is for performing intra prediction on the template region in the first intra prediction mode; and   determining an intra prediction value of the current block according to the first cost and the second cost;   wherein the first intra prediction mode is one of the at least two intra prediction modes or different from the at least two intra prediction modes.   
     
     
         2 . The method of  claim 1 , wherein determining the intra prediction value of the current block according to the first cost and the second cost comprises:
 determining the intra prediction value of the current block according to the at least two intra prediction modes and the first weight combination when the first cost is less than the second cost, wherein the intra prediction value of the current block is obtained by weighting, according to the first weight combination, prediction values obtained by performing intra prediction on the current block in the at least two intra prediction modes.   
     
     
         3 . The method of  claim 1 , wherein determining the intra prediction value of the current block according to the first cost and the second cost comprises:
 determining the intra prediction value of the current block according to the first intra prediction mode when the first cost is greater than or equal to the second cost.   
     
     
         4 . The method of  claim 1 , wherein determining, according to the at least two intra prediction modes and the first weight combination, the first cost for performing intra prediction on the template region of the current block in the at least two intra prediction modes comprises:
 obtaining at least two first prediction values by performing intra prediction on the template region in the at least two intra prediction modes;   obtaining a weighted result by weighting, according to the first weight combination, the at least two first prediction values; and   determining the first cost according to the weighted result and a reconstructed value of the template region.   
     
     
         5 . The method of  claim 1 , wherein determining, according to the first intra prediction mode, the second cost for performing intra prediction on the template region in the first intra prediction mode comprises:
 obtaining a second prediction value by performing intra prediction on the template region in the first intra prediction mode; and   determining the second cost according to the second prediction value and a reconstructed value of the template region.   
     
     
         6 . The method of  claim 1 , wherein determining the at least two intra prediction modes according to the derivation manner comprises:
 determining the at least two intra prediction modes according to a cost for performing intra prediction on the template region in a intra prediction mode when the derivation manner is template-based intra mode derivation (TIMD).   
     
     
         7 . The method of  claim 1 , wherein determining the at least two intra prediction modes according to the derivation manner comprises:
 determining the at least two intra prediction modes according to an amplitude value corresponding to a intra prediction mode on the template region when the derivation manner is decoder-side intra mode derivation (DIMD), wherein the amplitude value is obtained according to a sample gradient at at least one position in at least one direction in the template region.   
     
     
         8 . The method of  claim 1 , wherein the template region of the current block comprises at least part of samples in at least one row of samples at a top, a left, a top left, a bottom left, and a top right of the current block. 
     
     
         9 . An intra prediction method, applicable to an encoder and comprising:
 determining at least two intra prediction modes when an intra prediction value is determined in a derivation manner;   determining a first weight combination related to the at least two intra prediction modes;   determining a first cost according to the at least two intra prediction modes and the first weight combination, wherein the first cost is for performing intra prediction on a template region of a current block in the at least two intra prediction modes;   determining a second cost according to a first intra prediction mode, wherein the second cost is for performing intra prediction on the template region in the first intra prediction mode;   determining an intra prediction value of the current block according to the first cost and the second cost; and   signalling a prediction mode parameter in a bitstream, wherein the prediction mode parameter indicates that the intra prediction value is to be determined in the derivation manner;   wherein the first intra prediction mode is one of the at least two intra prediction modes or different from the at least two intra prediction modes.   
     
     
         10 . The method of  claim 9 , wherein determining the intra prediction value of the current block according to the first cost and the second cost comprises:
 determining the intra prediction value of the current block according to the at least two intra prediction modes and the first weight combination when the first cost is less than the second cost, wherein the intra prediction value of the current block is obtained by weighting, according to the first weight combination, prediction values obtained by performing intra prediction on the current block in the at least two intra prediction modes.   
     
     
         11 . The method of  claim 9 , wherein determining the intra prediction value of the current block according to the first cost and the second cost comprises:
 determining the intra prediction value of the current block according to the first intra prediction mode when the first cost is greater than or equal to the second cost.   
     
     
         12 . The method of  claim 9 , wherein determining, according to the at least two intra prediction modes and the first weight combination, the first cost for performing intra prediction on the template region of the current block in the at least two intra prediction modes comprises:
 obtaining at least two first prediction values by performing intra prediction on the template region in the at least two intra prediction modes;   obtaining a weighted result by weighting, according to the first weight combination, the at least two first prediction values; and   determining the first cost according to the weighted result and a reconstructed value of the template region.   
     
     
         13 . The method of  claim 9 , wherein determining, according to the first intra prediction mode, the second cost for performing intra prediction on the template region in the first intra prediction mode comprises:
 obtaining a second prediction value by performing intra prediction on the template region in the first intra prediction mode; and   determining the second cost according to the second prediction value and a reconstructed value of the template region.   
     
     
         14 . The method of  claim 9 , wherein determining the at least two intra prediction modes when the intra prediction value is determined in the derivation manner comprises:
 determining the at least two intra prediction modes according to a cost for performing intra prediction on the template region in a intra prediction mode when the derivation manner is template-based intra mode derivation (TIMD).   
     
     
         15 . The method of  claim 9 , wherein determining the at least two intra prediction modes when the intra prediction value is determined in the derivation manner comprises:
 determining the at least two intra prediction modes according to an amplitude value corresponding to a intra prediction mode on the template region when the derivation manner is decoder-side intra mode derivation (DIMD), wherein the amplitude value is obtained according to a sample gradient at at least one position in at least one direction in the template region.   
     
     
         16 . The method of  claim 9 , wherein the template region of the current block comprises at least part of samples in at least one row of samples at a top, a left, a top left, a bottom left, and a top right of the current block. 
     
     
         17 . A decoder, comprising:
 a memory configured to store computer programs; and   a processor configured to execute the computer programs stored in the memory to:
 obtain a prediction mode parameter, wherein the prediction mode parameter indicates that an intra prediction value is to be determined in a derivation manner; 
 determine at least two intra prediction modes according to the derivation manner; 
 determine a first weight combination related to the at least two intra prediction modes; 
 determine a first cost according to the at least two intra prediction modes and the first weight combination, wherein the first cost is for performing intra prediction on a template region of a current block in the at least two intra prediction modes; 
 determine a second cost according to a first intra prediction mode, wherein the second cost is for performing intra prediction on the template region in the first intra prediction mode; and 
 determine an intra prediction value of the current block according to the first cost and the second cost; 
 wherein the first intra prediction mode is one of the at least two intra prediction modes or different from the at least two intra prediction modes. 
   
     
     
         18 . The decoder of  claim 17 , wherein the processor is specifically configured to:
 determine the intra prediction value of the current block according to the at least two intra prediction modes and the first weight combination when the first cost is less than the second cost, wherein the intra prediction value of the current block is obtained by weighting, according to the first weight combination, prediction values obtained by performing intra prediction on the current block in the at least two intra prediction modes.   
     
     
         19 . The decoder of  claim 17 , wherein the processor is specifically configured to:
 determine the intra prediction value of the current block according to the first intra prediction mode when the first cost is greater than or equal to the second cost.   
     
     
         20 . The decoder of  claim 17 , wherein the processor is specifically configured to:
 obtain at least two first prediction values by performing intra prediction on the template region in the at least two intra prediction modes;   obtain a weighted result by weighting, according to the first weight combination, the at least two first prediction values; and   determine the first cost according to the weighted result and a reconstructed value of the template region.